Self-expanding stent delivery system with two sheaths

ABSTRACT

A medical device delivery system is disclosed which has a distal inner sheath and a distal outer sheath covering a medical device mounting region and any medical device mounted thereon. The outer sheath is designed to retain the medical device for lengthy periods of time while the inner sheath is designed to retain the sheath for shorter periods of time.

FIELD OF THE INVENTION

This invention relates to a stent delivery catheter system, such as thekind used in percutaneous transluminal coronary angioplasty (PTCA)procedures. More particularly, it relates to a stent delivery catheteremploying two retractable sheaths which may be retracted to release aself-expanding stent, a balloon assisted expandable stent or a balloonexpandable stent.

BACKGROUND OF THE INVENTION

In typical PTCA procedures, a guiding catheter is percutaneouslyintroduced into the cardiovascular system of a patient and advancedthrough the aorta until the distal end is in the ostium of the desiredcoronary artery. Using fluoroscopy, a guide wire is then advancedthrough the guiding catheter and across the site to be treated in thecoronary artery. An over the wire (OTW) balloon catheter is advancedover the guide wire to the treatment site. The balloon is then expandedto reopen the artery. The OTW catheter may have a guide wire lumen whichis as long as the catheter or it may be a rapid exchange catheterwherein the guide wire lumen is substantially shorter than the catheter.Alternatively, a fixed wire balloon catheter could be used. This devicefeatures a guide wire which is affixed to the catheter and cannot beremoved.

To help prevent arterial closure, repair dissection, or preventrestenosis, a physician can implant an intravascular prosthesis, or astent, for maintaining vascular patency inside the artery at the lesion.The stent may either be a self-expanding stent, a balloon assistedexpandable stent or a balloon expandable stent. For the latter type, thestent is often delivered on a balloon and the balloon is used to theexpand the stent. The self-expanding stents may be made of shape memorymaterials such as nitinol or constructed of regular metals but of adesign which exhibits self expansion characteristics.

In certain known stent delivery catheters, a stent and an optionalballoon are positioned at the distal end of the catheter, around a corelumen. The stent and balloon are held down and covered by a sheath orsleeve. When the distal portion is in its desired location of thetargeted vessel the sheath or sleeve is retracted to expose the stent.After the sheath is removed, the stent is free to self-expand or beexpanded with a balloon.

In a coronary stent deployment system which utilizes a retractablesheath one problem which is encountered is the interaction of the sheathand the stent upon retraction of the sheath. Typically, as the sheathslides off of the stent, the stent is subjected to potential marring bythe sheath. While this problem can be minimized by making the sheath ofsoft materials, such materials are often unsuitable for use with aself-expanding stent where prolonged storage results in creepdeformation of the inner sheath.

It is desirable to provide a medical device delivery system whichprovides a protective, non-marring inner sheath for the medical deviceand is capable of retaining the medical device for brief periods of timeand which further has an additional outer sheath over the inner sheathwhich is capable of retaining the medical device for lengthy periods oftime, thereby allowing the device to have a suitable shelf life.

SUMMARY OF THE INVENTION

The present invention provides a medical device delivery system in whichtwo sheaths, an inner sheath and an outer sheath, cover a medical devicemounted on the distal end of the medical device delivery system. In itsvarious embodiments, the invention contemplates a delivery system inwhich the inner sheath is either a tear away sheath or a retractablesheath and the outer sheath is either a retractable sheath or a pullaway sheath.

In accordance with the present invention, the outer sheath is desirablyconstructed to be more creep resistant than the inner sheath. The outersheath may be made of a material having a higher hoop strength than theinner material. The inner material should be capable of retaining themedical device in place on the delivery system for at least a shortperiod of time before it either is retracted or opens due to materialfailure. The outer sheath should be capable of retaining the medicaldevice for longer periods of time so that the device may have areasonable shelf life.

To this end, the invention provides a medical device delivery systemcomprising a manifold at the proximal end of the delivery system.Extending distally from the manifold is an inner tube. At the distal endof the inner tube is a medical device mounting region for concentricallymounting a medical device thereon. Covering the medical device mountingregion, at least in part, is a distal inner sheath attached to the innertube at the distal region of the inner tube. The distal inner sheath isconcentrically disposed about the inner tube. The medical devicedelivery system also comprises a distal outer sheath, concentricallydisposed about the inner tube. At least a portion of the distal outersheath is disposed about at least a portion of inner sheath.

In one embodiment of the invention, the distal inner sheath is a tearaway sheath and the distal outer sheath is retractable by means of anouter sheath retraction device. The outer sheath retraction deviceextends in a distal direction from the manifold. The distal outer sheathextends from the distal end of the retraction device.

In another embodiment of the invention, the distal inner sheath isretractable by means of an inner sheath retraction device. The innersheath retraction device extends in a distal direction from themanifold. The distal inner sheath extends from the distal end of theinner sheath retraction device. Similarly, the outer sheath isretractable by means of an outer sheath retraction device. The outersheath retraction device extends in a distal direction from themanifold. The distal outer sheath extends from the distal end of theouter sheath retraction device.

In another embodiment of the invention, the distal inner sheath isretractable by means of an inner sheath retraction device. The innersheath retraction device extends in a distal direction from themanifold. The distal inner sheath extends from the distal end of theinner sheath retraction device. The distal outer sheath contacts theinner sheath, and extends proximally from the distal region of the innertube. The distal outer sheath is removed prior to insertion of thedevice in the body.

In all of the embodiments, the delivery system may further comprise themedical device mounted on the medical device mounting region. Among thecontemplated medical device for use with this system are stents andgrafts. Desirably, the stent will be self-expanding or a balloonassisted expandable stent.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a longitudinal cross-sectional view of an embodiment of theinventive medical device delivery system.

FIG. 2 shows a partial cut-away perspective view of the distal end ofthe embodiment of FIG. 1.

FIG. 3 shows an enlarged view of region 3 of the medical device deliverysystem of FIG. 1.

FIG. 4 shows a longitudinal cross-sectional view of an embodiment of theinventive medical device delivery system.

FIG. 5 shows a longitudinal cross-sectional view of an embodiment of theinventive medical device delivery system.

FIG. 6 shows a perspective view of a stent for use with the inventivemedical device delivery system.

FIG. 7 shows a perspective view of a graft for use with the inventivemedical device delivery system.

FIG. 8 shows a side elevational view of a vena cava filter for use withthe inventive medical device delivery system.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

The present invention provides a medical device delivery system in whichthe medical device is contained and/or surrounded and/or protected byboth an inner sheath and an outer sheath.

In several of the embodiments, the inner sheath is a tear away sheath.The presence of a tear away inner sheath protects the medical devicefrom being marred upon the sliding removal of the outer sheath. Afterthe outer sheath is removed, the inner tear away sheath, no longercontained by the outer sheath, opens as a result of the expanding forceof the self-expanding, balloon assisted or balloon expandable medicaldevice.

Turning to the figures, FIG. 1 shows one embodiment of the inventivemedical device delivery system generally at 110. The medical devicedelivery system 110 has a proximal end and a distal end and comprises amanifold 120 located at the proximal end of delivery system 110.Extending in a distal direction from manifold 120 is an inner tube 124having a distal region 128 and a proximal region 132. At the distalregion of inner tube 124 is a medical device mounting region 136 forconcentrically mounting a medical device thereon. Delivery system 110further comprises a distal inner sheath 140 attached to inner tube 124at distal region 128. Distal inner sheath 140 is concentrically disposedabout inner tube 124 and covers at least a portion, desirably asubstantial portion and more desirably the entirety of medical devicemounting region 136 to retain a medical device about the medical devicemounting region. Inner sheath 140 is fixedly attached to the medicaldevice delivery system and desirably is mounted to the inner tube. Asshown in FIG. 2, distal inner sheath 140 is a perforated 137 or scoredtear away sheath. A distal outer sheath 144 is concentrically disposedabout inner tube 124 and at least a portion of distal outer sheath 144is disposed about at least a portion of distal inner sheath 140. Thedevice further comprises an outer sheath retraction device 148 whichextends in a distal direction from manifold 120. Distal outer sheath 144is seen to extend from the distal end of outer sheath retraction device148.

Although there are a variety of outer sheath retraction devices that maybe used in the practice of the invention, as shown in FIGS. 1 and 3, apreferred outer sheath retraction device 148 comprises a proximal outertube 152, a collapsible sheath 156 extending from the distal end ofproximal outer tube 152 and a distal outer tube 160. The proximal end ofdistal outer tube 160 extends from the distal end of the collapsiblesheath 156. A slidable pull wire 164 extends from manifold 120 to distalouter sheath 144. In use, the distal end of retraction device 148 movesin a proximal direction upon sliding pull wire 164 proximally therebyretracting distal outer sheath 144. Tear away inner sheath 140 may thenopen as a result of the force of the expansion of the expandable medicaldevice. Because the tear away inner sheath is fixedly attached to themedical device delivery system, the tear away inner sheath is withdrawnfrom the body of the medical device delivery system is withdrawn.

The stent delivery system may, optionally, further comprise a medicaldevice mounted on the medical device mounting region 136. While avariety of medical devices are contemplated, in the embodiment shown inFIGS. 1 and 2, the medical device is a self-expanding stent 168.

In another embodiment of the inventions, as shown in FIG. 4, thedelivery system, shown generally at 210, comprises a manifold 220, aninner tube 224 having a distal region 228, a proximal region 232 and amedical device mounting region 236 for concentrically mounting a medicaldevice thereon as in the previous embodiment. Similarly, as in theprevious embodiment, delivery system 210 further comprises a distalinner sheath 240. Distal inner sheath 240 is concentrically disposedabout inner tube 224 and covers at least a portion of medical devicemounting region 236. Unlike in the previous embodiment, delivery system210 further comprises a inner sheath retraction device 241 having adistal end and a proximal end. Inner sheath retraction device 241,consists of pull collar 243 mounted on proximal end of distal end ofinner sheath 240 and a pull wire 245 extending distally from manifold220 to pull collar 243.

As in the previous embodiment, a distal outer sheath 244 isconcentrically disposed about inner tube 224. At least a portion ofdistal outer sheath 244 is disposed about at least a portion of distalinner sheath 240. Also, the device comprises an outer sheath retractiondevice 248 comprising a proximal outer tube 252, a collapsible sheath256 and a distal outer tube 260 as described for the embodiment of FIGS.1-3. The collapsible sheath section of the medical device deliverysystem is similar to that shown in FIG. 3, differing only in thepresence of an additional wire, corresponding to a slidable pull-wireoperably associated with the inner sheath. Slidable wire 264 extendsfrom manifold 220 to distal outer sheath 244 and in use, the outersheath retraction device works in a manner identical to that describedfor the outer sheath retraction device described above. Alternatively,although not shown in FIG. 4, inner sheath 240 may also be retracted viaa collapsible retraction device similar to retraction device 248 used toretract outer sheath 244.

Also shown is an optional medical device in the form of a self-expandingstent 268 mounted on the medical device mounting region 236.

In another embodiment, the invention comprises a medical device deliverysystem shown generally at 310 in FIG. 5. Medical device delivery system310, as in the previous embodiments, comprises a manifold 320, an innertube 324 having a distal region 328, a proximal region 332 and a medicaldevice mounting region 336 for concentrically mounting a medical devicethereon. Delivery system 310 further comprises a distal inner sheath340. Distal inner sheath 340 is concentrically disposed about inner tube324 and covers at least a portion of medical device mounting region 336.As in the embodiment of FIG. 4, delivery system 310 further comprises ainner sheath retraction device 341 having a distal end and a proximalend. Inner sheath retraction device 341, consists of pull collar 343mounted on proximal end of distal end of inner sheath 340 and a pullwire 345 extending distally from manifold 320 to pull collar 343.

As in the previous embodiments, a distal outer sheath 344 (in sock form)is concentrically disposed about inner tube 324. At least a portion ofdistal outer sheath 344 is disposed concentrically about at least aportion of distal inner sheath 340. Unlike in any of the previousembodiments, distal outer sheath 344 extends proximally from the distalend of the inner tube and is removable by sliding the distal outersheath in a distal direction. Distal outer sheath 344 is in contact withdistal inner sheath 340. Mounted concentrically about the inner tube andcarrying the pull wire is outer tube 360. Although distal outer sheath344 is depicted in FIG. 5 as being closed at the distal end, it mayoptionally be open at the distal end. In use, distal outer sheath 344 isremoved prior to insertion of the medical device delivery system intothe body. A removable sheath such as that disclosed in U.S. Pat. No.5,800,517 to Anderson et al., incorporated herein in its entirety byreference, may be used.

Also shown is an optional medical device in the form of a self-expandingstent 368 mounted on the medical device mounting region 336.

In another embodiment, not shown, the medical device delivery system issubstantially similar to that shown in FIG. 5 differing only in that theretraction device for retracting the inner sheath is a collapsiblesheath as shown in FIGS. 1 and 3.

In the various embodiments of the invention, suitable manifolds, as areknown in the art, may be employed. In the embodiment containing tworetractable sheaths, the manifold must be able to accommodate tworetraction mechanism. In the other embodiments in which one retractiondevice is employed, the manifold must be able to accommodate oneretraction device.

The inner tubes employed in the various embodiments may be made ofsuitable materials as are known in the art including. Preferably, theinner tubes are made of flexible, but incompressible construction suchas a polymer encapsulated braid or coil. Such construction is known inthe art. The braid/coil may be comprised of stainless steel encased in apolymer such as Polyimide with an inner layer of Teflon.

The pull collars attached to the retractable sheaths may suitably beringshaped members made of stainless steel affixed to the interior ofthe retractable sheaths by an appropriate adhesive such as Loctite 4011,a cyanoacrylate. Desirably, the pull collar will be made of aradio-opaque material such as gold.

The outer sheath, desirably will be made of a material which hassufficient strength to contain a self-expanding stent in the stent'sunexpanded configuration. It is desirable that the outer sheath beconstructed so as to be creep resistant. It is also highly desirablethat the inner sheath be constructed to be less creep resistant than theouter sheath.

Some of the benefits of the present invention may also be realized in asystem wherein the outer sheath is made of a thicker material than theinner sheath.

Suitable materials for the outer sheath include polyimide, Pebax,polyethylene, Nylon, and metal for the embodiments in which the outersheath is retractable via a retraction device extending to the manifold.Suitable materials for the sock-like distal outer sheath includepolyimide, Pebax, polyethylene, Nylon, and metal. As for the distalinner sheath, suitable materials include PTFE, Pebax, polyurethane,polyethylene, and polyimide for the tear away embodiments and for theretractable distal inner sheath embodiments.

The invention also contemplates the use of porous materials for theinner and outer sheaths thereby allowing for the inflow of bodily fluidsinto the medical device mounting region. This can be helpful in primingthe medical device by forcing out any air in the region of the medicaldevice. Suitable porous materials include Suitable porous materialsinclude expanded polytetrafluoroethylene (ePTFE), polyester andsilicone. Desirably, the materials will have a pore size ranging from0.01 mm to 5.0 mm.

Although the tear away sheath has been described as being mechanicallyreleased by the force of the expanding medical device, the inventionalso contemplates the use of a tear away sheath which is hydrolyticallyreleased. The sheath may be ‘glued’ shut via a bio-compatible watersoluble material. The sheath may then be opened by supplying waterthereto so as to dissolved the ‘glue’. Optionally, the glue may bechosen such that it is stable in the presence of fluids at bodilytemperatures by dissolves upon exposure to a fluid of slightly elevatedtemperature such as water at a temperature of 42° C. Alternatively, thesheath may be glued shut via a material which is releasable via actinicenergy such as ultraviolet radiation or gamma radiation suppliedthereto.

The distal inner and outer sheaths may be bonded to the inner tubeand/or retraction devices by the use of suitable adhesives includingLoctite 4011, a cyanoacrylate as well as methacrylate, or H.B. Fuller3507, a urethane adhesive. Other suitable bonding methods includepressure welding, heat welding and laser welding.

The invention also contemplates the use of various lubricants on atleast a portion of one or more of the inner and outer sheaths tofacilitate the relative motion of the inner and outer sheaths uponretraction or removal of the outer sheath. As seen in FIG. 2, distalinner sheath 140 has an inner surface facing the inner tube and an outersurface 138 facing distal outer sheath 144. Similarly, distal outersheath 144 has an inner surface 146 facing distal inner sheath 140 andan outer surface facing outward. A lubricant may applied to at least aportion of at least one of outer surface 138 of inner sheath 140 orinner surface 146 of outer sheath 144 so as to reduce frictional forcesbetween the two sheathes. The lubricant may be applied selectively tothe surfaces or, alternatively, may be applied to the entirety of thesurfaces.

Although the inner surface and outer surface to which lubricants may beapplied have been highlighted in FIG. 2, it is understood that theinvention provides for the similar use of such lubricants on the outersurface of the inner sheath and the inner surface of the outer sheath inthe other embodiments as well.

In all of the above embodiments, a lubricant may, optionally, be appliedto at least a portion of the inner wall and/or outer wall. Suitablelubricants include silicones, PVP (polyvinyl pyrrolidone), PPO(polypropylene oxide) and PEO. Additionally, BioSlide™ coating producedby SciMed made be used as well. BioSlide™ is a hydrophilic, lubriciouscoating comprising polyethylene oxide and neopentyl glycol diacrylatepolymerized in a solution of water and isopropyl alcohol in the presenceof a photoinitiator such as azobisisobutronitrile.

Additional details of the design of embodiments of the inventive medicaldevice delivery system which employ collapsible sheaths, in particularthe portion of the device proximal to the inner sheath may be found inthe various embodiments disclosed in U.S. Pat. No. 5,534,007 to St.Germain and Olson, incorporated herein in its entirety by reference.

In addition to the use of a collapsible sheath retraction device forretracting the outer sheath, the invention also contemplates the use ofother suitable retraction means as are known in the art includingslidably sealed retractable sheaths and midshaft seals as described inco-pending commonly assigned U.S. patent application Ser. No. 08/722,834filed Sep. 27, 1996 now U.S. Pat. No. 5,772,669, and acontinuation-in-part application Ser. No. 09/071,484 filed May 1, 1998now U.S. Pat. No. 5,957930. The entire contents of both applications arehereby incorporated in their entirety by reference. Other contemplatedretraction means include sheaths activated directly by pull-collars asdescribed in U.S patent application Ser. No. 09/071,484 filed May 27,1998, now U.S. Pat. No. 5,7957,930, and screw-like retraction devices asdescribed in U.S. Pat. No. 5,201,757 to Heyn et al. all of which areincorporated herein in their entirety by reference.

Although the medical device shown in the figures have all been describedas self-expanding stents, other mechanically expandable stents may beused as well, including balloon expandable stents. A perspective view ofone suitable stent is shown in FIG. 6 at 668. Other medical devicessuitable for delivery with the present delivery system include implantssuch as grafts and vena cava filters. A suitable graft is shown in FIG.7 at 768 while a suitable vena cava filter is shown in FIG. 8 at 868.

As shown in the figures, the medical device delivery systems may furthercomprise other optional features, as are known in the art, such asbumpers 172, 272, 372 and 472 and markers 176, 276, 376 and 476. Bumpers172-472 may be made of polyethylene and are affixed to inner tube 124 byadhesive such as H.B. Fuller 3507. Marker bands 176-476 are preferablymade of a radio-opaque material such as gold although other materialssuch as stainless steel may be used as well. The markers are included toaid in positioning and may be affixed to inner tube 124 by adhesive suchas Loctite 4011.

While several specific embodiments of the present invention have beendescribed, the invention is directed more generally toward the inclusionof two sheaths in any other suitable catheter design not specificallydescribed herein including fixed wire, over-the-wire and rapid-exchangecatheters.

In the case of the fixed-wire design, the guidewire is fixedly attachedto the medical device delivery system. A fixed-wire delivery system isdescribed in U.S. Pat. No. 5,702,364 to Euteneuer et al., incorporatedherein in its entirety by reference, and may be suitably modified foruse with the inventive medical device delivery system.

In an over-the-wire embodiment, the inner tube extends proximally to amanifold and a guide wire may be inserted into the inner tube from theproximal end, the guide wire extending to the distal end of the system.The medical device delivery system may then ride on the guidewire.

Similarly, a rapid exchange delivery system is described in U.S. Pat.No. 5,534,007 to St. Germain et al., incorporated herein in its entiretyby reference, and may be suitably modified for use with the inventivemedical device delivery system. Specifically, the rapid-exchange versionmay be realized by terminating the inner tube in a guide wire port in alocation along the system distal to the proximal end of the system toallow for insertion of a guide wire therein. In the rapid-exchangeembodiment, only a portion of the medical device delivery system rideson a guidewire. Typically, the usable length of the medical devicedelivery system is approximately 135 cm. For a rapid-exchange medicaldevice delivery system, the distance from where the guide wire accessesthe inner tube to the distal tip will be approximately 5 cm to 35 cm.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is:
 1. A medical device delivery system having aproximal end and a distal end comprising: an inner tube having a distalregion and a proximal region and a medical device region at the distalregion for disposing a medical device thereabout; a distal inner sheathdisposed about at least a portion of the medical device region, an innersheath retraction device extending from the distal inner sheath to theproximal end of the medical device delivery system; a distal outersheath disposed about at least a portion of the medical device region;and an outer sheath retraction device extending from the distal outersheath to the proximal end of the medical device delivery system whereinthe distal inner sheath is constructed to be less creep resistant thanthe distal outer sheath.
 2. The medical device delivery system of claim1 wherein the retraction device comprises a pull-collar with a pull wireattached thereto.
 3. The medical device delivery system of claim 1wherein at least one of the inner sheath and the outer sheath is made ofa porous material.
 4. The medical device delivery system of claim 1further comprising a medical device selected from the group consistingof stents, grafts and vena cava filters, the medical device disposedabout the medical device region.
 5. The medical device delivery systemof claim 4 wherein the medical device is a stent.
 6. The medical devicedelivery system of claim 5 wherein the stent is self-expandable.
 7. Amedical device delivery system having a proximal end and a distal endcomprising: an inner tube having a distal region and a proximal regionand a medical device region at the distal region for disposing a medicaldevice thereabout; a distal inner sheath disposed about at least aportion of the medical device region, an inner sheath retraction deviceextending from the distal inner sheath to the proximal end of themedical device delivery system; a distal outer sheath disposed about atleast a portion of the medical device region; and an outer sheathretraction device extending from the distal outer sheath to the proximalend of the medical device delivery system wherein the distal outersheath is made of a thicker material than the distal inner sheath.
 8. Amedical device delivery system having a proximal end and a distal endcomprising: an inner tube having a distal region and a proximal regionand a medical device region at the distal region for disposing a medicaldevice thereabout; a distal inner sheath disposed about at least aportion of the medical device region, an inner sheath retraction deviceextending from the distal inner sheath to the proximal end of themedical device delivery system; a distal outer sheath disposed about atleast a portion of the medical device region; and an outer sheathretraction device extending from the distal outer sheath to the proximalend of the medical device delivery system wherein the distal innersheath is a perforated tear away sheath.
 9. A medical device deliverysystem having a proximal end and a distal end comprising: an inner tubehaving a distal region and a proximal region and a medical device regionat the distal region for disposing a medical device thereabout; a distalinner sheath disposed about at least a portion of the medical deviceregion, an inner sheath retraction device extending from the distalinner sheath to the proximal end of the medical device delivery system;a distal outer sheath disposed about at least a portion of the medicaldevice region; and an outer sheath retraction device extending from thedistal outer sheath to the proximal end of the medical device deliverysystem wherein the outer sheath retraction device comprises: a proximalouter tube having a distal end; a collapsible sheath having a proximalend and a distal end, the proximal end of the collapsible sheathextending from the distal end of proximal outer tube; a distal outertube having a proximal end and a distal end, the proximal end of thedistal outer tube extending from the distal end of the collapsiblesheath; and a slidable pull wire extending proximally from the distalouter sheath, whereby the distal end of the retraction device moves in aproximal direction on sliding the pull wire proximally.
 10. A medicaldevice delivery system having a proximal end and a distal endcomprising: an inner tube having a distal region and a proximal regionand a medical device region at the distal region for disposing a medicaldevice thereabout; a distal inner sheath disposed about at least aportion of the medical device region, an inner sheath retraction deviceextending from the distal inner sheath to the proximal end of themedical device delivery system; a distal outer sheath disposed about atleast a portion of the medical device region; and an outer sheathretraction device extending from the distal outer sheath to the proximalend of the medical device delivery system wherein the distal innersheath has an inner surface facing the inner tube and an outer surfacefacing the distal outer sheath and the distal outer sheath has an innersurface facing the distal inner sheath and an outer surface facingoutward and a lubricant is applied to at least a portion of at least oneof the outer surface of the distal inner sheath or the inner surface ofthe distal outer sheath so as to reduce frictional forces between thedistal inner sheath and the distal outer sheath.
 11. A stent deliverysystem having a proximal end and a distal end comprising: an inner tubewith a distal region and a proximal region and a stent disposal regionat the distal region for disposing a stent thereabout; a distal innersheath disposed about the inner tube and covering the stent disposalregion; an inner sheath retraction device having a distal end and aproximal end, the inner sheath retraction device extending proximallyfrom the distal inner sheath; a distal outer sheath at least a portionof the outer sheath disposed about the stent disposal region; and anouter sheath retraction device having a distal end and a proximal end,the outer sheath retraction device extending proximally from the distalouter sheath wherein the distal inner sheath is constructed to be lesscreep resistant than the distal outer sheath.
 12. A stent deliverysystem having a proximal end and a distal end comprising: an inner tubewith a distal region and a proximal region and a stent disposal regionat the distal region for disposing a stent thereabout; a distal innersheath disposed about the inner tube and covering the stent disposalregion; an inner sheath retraction device having a distal end and aproximal end, the inner sheath retraction device extending proximallyfrom the distal inner sheath; a distal outer sheath at least a portionof the outer sheath disposed about the stent disposal region; and anouter sheath retraction device having a distal end and a proximal end,the outer sheath retraction device extending proximally from the distalouter sheath wherein the distal outer sheath is made of a thickermaterial than the distal inner sheath.
 13. The stent delivery system ofclaim 12 wherein the inner sheath retraction device comprises apull-collar with a pull wire attached thereto.
 14. The stent deliverysystem of claim 12 wherein at least one of the inner sheath and theouter sheath is made of a porous material.
 15. The stent delivery systemof claim 12 further comprising a stent disposed about the medical deviceregion.
 16. The stent delivery system of claim 5 wherein the stent isballoon expandable.
 17. The stent delivery system of claimed wherein thestent is self-expandable.
 18. A stent delivery system having a proximalend and a distal end comprising: an inner tube with a distal region anda proximal region and a stent disposal region at the distal region fordisposing a stent thereabout; a distal inner sheath disposed about theinner tube and covering the stent disposal region; an inner sheathretraction device having a distal end and a proximal end, the innersheath retraction device extending proximally from the distal innersheath; a distal outer sheath at least a portion of the outer sheathdisposed about the stent disposal region; and an outer sheath retractiondevice having a distal end and a proximal end, the outer sheathretraction device extending proximally from the distal outer sheathwherein the outer sheath retraction device comprises: a proximal outertube having a distal end; a collapsible sheath having a proximal and adistal end, the proximal end of the collapsible sheath extending fromthe distal end of proximal outer tube; a distal outer tube havingproximal and distal ends, the proximal end of the distal outer tubeextending from the distal end of the collapsible sheath; and a slidablepull wire extending proximally from the distal outer sheath, whereby thedistal end of the retraction device moves in a proximal direction onsliding the pull wire proximally.
 19. A stent delivery system having aproximal end and a distal end comprising: an inner tube with a distalregion and a proximal region and a stent disposal region at the distalregion for disposing a stent thereabout; a distal inner sheath disposedabout the inner tube and covering the stent disposal region; an innersheath retraction device having a distal end and a proximal end, theinner sheath retraction device extending proximally from the distalinner sheath; a distal outer sheath at least a portion of the outersheath disposed about the stent disposal region; and an outer sheathretraction device having a distal end and a proximal end, the outersheath retraction device extending proximally from the distal outersheath wherein the inner sheath has an inner surface facing the innertube and an outer surface facing the distal outer sheath and the distalouter sheath has an inner surface facing the distal inner sheath and anouter surface facing outward and a lubricant is applied to at least aportion of at least one of the outer surface of the distal inner sheathor the inner surface of the distal outer sheath so as to reducefrictional forces between the distal inner sheath and the distal outersheath.
 20. A medical device delivery system having a proximal and adistal end comprising: an inner tube with a distal region and a proximalregion, the inner tube having a medical device region at the distalregion for disposing a medical device thereabout; a distal inner scoredtear away sheath disposed about the inner tube and covering at least aportion of the medical device region; and a distal outer sheath,disposed about the distal inner scored tear away sheath and an outersheath retraction device having a distal end and a proximal end, theouter sheath retraction device extending proximally from the distalouter sheath wherein the distal inner scored tear away sheath isconstructed to be less creep resistant than the distal outer sheath. 21.The medical device delivery system of claim 20 wherein the distal outersheath is constructed to be creep resistant.
 22. The medical devicedelivery system of claim 20 wherein the retraction device comprises apull-collar with a pull wire attached thereto.
 23. The medical devicedelivery system of claim 20 wherein at least one of the distal innerscored tear away sheath and the distal outer sheath is made of porousmaterial.
 24. The medical device delivery system of claim 20 furthercomprising a medical device selected from the group consisting ofstents, grafts and vena cava filters, the medical device disposed aboutthe medical device region.
 25. The medical device delivery system ofclaim 24 wherein the medical device is a stent.
 26. The medical devicedelivery system of claim 25 wherein the stent is self-expandable.
 27. Amedical device delivery system having a proximal and a distal endcomprising: an inner tube with a distal region and a proximal region,the inner tube having a medical device region at the distal region fordisposing a medical device thereabout; a distal inner scored tear awaysheath disposed about the inner tube and covering at least a portion ofthe medical device region; and a distal outer sheath, disposed about thedistal inner scored tear away sheath and an outer sheath retractiondevice having a distal end and a proximal end, the outer sheathretraction device extending proximally from the distal outer sheathwherein the distal outer sheath is made of a thicker material than thedistal inner scored tear away sheath.
 28. A medical device deliverysystem having a proximal and a distal end comprising: an inner tube witha distal region and a proximal region, the inner tube having a medicaldevice region at the distal region for disposing a medical devicethereabout; a distal inner scored tear away sheath disposed about theinner tube and covering at least a portion of the medical device region;and a distal outer sheath, disposed about the distal inner scored tearaway sheath and an outer sheath retraction device having a distal endand a proximal end, the outer sheath retraction device extendingproximally from the distal outer sheath wherein the distal inner scoredtear away sheath has an inner surface facing the inner tube and an outersurface facing the distal outer sheath and the distal outer sheath hasan inner surface facing the distal inner scored tear away sheath and anouter surface facing outward and a lubricant is applied to at least aportion of at least one of the outer surface of the distal inner scoredtear away sheath or the inner surface of the distal outer sheath so asto reduce frictional forces between the distal outer sheath and thedistal inner scored tear away sheath.
 29. In a stent delivery systemcomprising a first retractable sheath carried over a stent, the firstretractable sheath having an associated retraction device, theimprovement being a second retractable sheath carried over the firstretractable sheath, the second retractable sheath having an associatedretraction device, the first retractable sheath constructed to be lesscreep resistant than the second retractable sheath.